I found him eating a turbo snail. He must have came in with the florida live rock.
Sorry about the picture quality. I tried to enhance it a little bit with a photo editor so you could see the crab better. He is right in the middle of the picture.
I do not see the picture but if its a "hairy" crab then its a rock crab. I got a few in my tampa bay rock. Catch them and relocate them. They are pure evil! I had one that was 4 inches wide from leg tip to leg tip kill a yellow tang as well as corals and anything else it could get its claws on. If it is a red crab that looks similar to an emerald crab keep your eye on them as well.